In vivo confocal microscopy has enormous potential to be used in a large number of physiological and pathological ocular conditions.
Editor’s Note: In vivo confocal microscopy is no longer only a research tool. It has important potentially sight-saving clinical applications. Confocal microscopy must be done if Acanthamoeba keratitis or fungal keratitis is being considered in the differential diagnosis. Culture results take too long. Early diagnosis is the key to a favorable result.
—Ernest W. Kornmehl, MD
Ophthalmologists face the challenge of differentiating among multiple clinical entities, with clinical suspicion initially often guiding treatment. Patient history and slit lamp examination are often the only tools available for diagnosis and monitoring of treatment.
A number of new imaging technologies have emerged in research and clinical ophthalmology.
Among these, in vivo confocal microscopy (IVCM) is a novel, noninvasive, high-resolution tool that allows imaging of the living ocular structures at the cellular level. Provision of images comparable to histochemical methods by IVCM, enables clinicians to study epithelial cells, keratocytes, endothelial cells, nerves, and immune cells in different ocular and systemic diseases, many of which are not visible by slit lamp examination (Figure 1).
Recently, the indications for IVCM have been significantly expanded beyond an adjunct tool in diagnosis of Acanthamoeba and fungal keratitis, and there have been numerous publications showing the utility of IVCM in various conditions, some of which have been summarized below.
Although cultures remain the gold standard for the diagnosis of causative microorganisms in infectious keratitis, they suffer from high false-negative rates and a significant delay in obtaining the results, particularly in cases of slow-growing organisms, such as fungi and Acanthamoeba. Given the importance of timing in diagnosis and initiation of anti-microbial therapy, there is an exciting emerging role for IVCM evolving not only for the diagnosis of microbial keratitis, but also potentially in the management of this disease.
The initial presentation of Acanthamoeba keratitis (AK) is typically nonspecific, often leading to misdiagnosis of patients and delay in appropriate therapy, in part due to poor yield and delay of positive cultures.